In the 1800's, which is around the same time that ice cubes started to be used in drinks, two bars tools started to show up behind the bar. The first was the Julep strainer and the other was a Hawthorne strainer.
The Julep strainer most likely evolved from the invention of the slotted spoon. The intent of the slotted spoon was to place the spoon over the top of a drink to keep the ice from hitting your teeth as you sipped your cocktail and later it was used to pour your drink into your glass while preventing the ice from splashing down. The need for the spoon quickly made obsolete when the straw was introduced to the world.
The Hawthorne strainer was named by the Boston bar where it originated as universal sized strainer. The spring like action made it possible to use over the rim of any sized glass and the perforated top made it possible to pour through.
The intent of use of both of these is questionable... some people say that you can only use the Julep strainer for stirred drinks and the Hawthorne for shaken drinks. Personally, I've seen both used interchangeably and i mix and match all the time. If it works.... it works!!